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Center for Nonlinear Studies |
A serious obstacle impeding the application of low- and high- temperature superconductor devices is the presence of trapped magnetic flux: flux lines or vortices can be induced by fields as small as the Earth's magnetic field. Once present, vortices dissipate energy and generate internal noise, limiting the operation of numerous superconducting devices. One method used to overcome this difficulty is by means of Ratchet Effect. A single particle confined in an asymmetric potential demonstrates and anticipated ratchet effect by drifting along the easy ratchet direction when subjected to non-equilibrium fluctuations. Here we studied the configurations, dynamics and depinning properties of vortex lattices interacting with asymmetric pinning potentials. The ratchet effect is observed as anticipated and we identified three different phases where there is no ratchet effect, normal ratchet effect and reduced ratchet effect. We also observed periodic structures in the ratchet effect when we vary the frequency of external AC driving current. By increasing the vortex density in the system, the vortex-vortex interaction begins to play an important role in the dynamics of vortices, which leads to the reversal ratchet effect at high vortex density.
Host: Nataili Gulbahce & Praveen Ramaprabhu